Mr Abbott said the men would be "arrested, prosecuted and jailed" should they return home, because they could easily "become a terrorist in Australia".

"A crime is a crime is a crime," Mr Abbott said.

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"If you go abroad to break Australian law, if you go abroad to kill innocent people in the name of misguided fundamental extremism, if you go abroad to be an Islamist killer, well we are hardly going to welcome you back into this country," he said.

Returning jihadists could face up to 25 years prison if found to have fought with a prescribed terror group, or found to have been in areas of Syria and Iraq banned under new anti-terror laws.

Talks with at least two of the men began several months ago, and one has engaged a Melbourne-based lawyer in a sign of the complexities involved with negotiating any return.

A former health worker from Victoria, believed to be named Abu Ibrahim, is reportedly among the three men wanting to return after becoming disillusioned with jihad.

Melbourne-based lawyer Rob Stary told Fairfax radio station 3AW on Tuesday he was representing a Victorian man in the matter, but would not confirm his client's name.

He said his client, an Australian-born convert to Islam, was prepared to face the full force of the law upon his return and wanted to use his experience to discourage would-be jihadists from joining the terror group.

"Firstly, if he comes back he will face whatever offence he is alleged to have committed and he'll be dealt with according to law here," Mr Stary said.

"We're not naive enough to suggest that he receive any indemnification, or that he should not be charged with appropriate offences. If he's engaged particularly in combat, or militarily in any way, then there's an expectation he'd be charged."

Mr Stary said his client was a trained medic who began working in a camp controlled by the Free Syrian Army, or an offshoot of that organisation.

"Now he says, 'I've seen what I've seen and I want to return home', and we're just trying to engage federal police particularly in a program that might see him provide some benefit to the community here, both in terms of de-radicalisation and probably intelligence," Mr Stary said.

"If he's capable of reclamation then we should utilise him, we should at least engage in the discussion, but the shutters have been put up by the [Australian Federal Police].

"I don't know what the intelligence community knows about him, [but] we know there has been an 'adverse assessment' of him. I'm certain the intelligence community would want to speak to him."